Electrolyte Disorders USMLE Step 1 Practice Question
A 72-year-old woman is brought to the emergency department because of progressive confusion and a generalized tonic clonic seizure. She recently started a thiazide diuretic for hypertension. Physical examination shows no edema and moist mucous membranes. Laboratory studies show sodium 116 mEq/L, potassium 3.6 mEq/L, serum osmolality 258 mOsm/kg, and urine osmolality 520 mOsm/kg. Which of the following is the most likely cause of this patient symptoms?
Answer choices
- AHypocalcemia causing neuromuscular hyperexcitability
- BSevere hyponatremia causing cerebral edemaCorrect answer
- CHyperkalemia causing cardiac membrane instability
- DSevere hypernatremia causing neuronal dehydration
- EHypermagnesemia causing central nervous system depression
- FThiazide-induced hypokalemia causing increased neuronal excitability
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